Coronary angioplasty. Coloured X-ray angiogram of a balloon catheter and stent (orange) being placed within a coronary artery of a heart. They will be used to treat stenosis (narrowing) of the artery. The flexible catheter used to place them there is seen snaking down from top left. The inflation of the balloon catheter will expand the artery and restore normal blood flow. The stent is a hollow tube mesh, expanded by the balloon catheter, that stays in the artery and supports it after the balloon catheter has been withdrawn. Arterial stenosis may arise from arterial disease. X-ray angiography injects a radio-opaque contrast medium to highlight blood vessels on X-rays.